The Note: Adultery allegations undercut Trump's authority

WASHINGTON, D.C. -- The TAKE with MaryAlice Parks

The Trump administration started the week attempting to bolster its authority on the world stage - only to have allegations of adultery continue to erode its credibility at home.

The White House’s retaliatory steps against the Kremlin Monday were sweeping and noteworthy. The president’s spokesperson said plainly that the Russian government’s behavior would not be tolerated, and lawmakers from both sides and international partners around the world applauded.

But this West Wing seems to be standing in quicksand.

The same day the White House tried to meet Russian aggression with decisive steps and bold rhetoric, it struggled under the weight of the salacious accusations regarding the president’s personal life and the actions of his lawyer in the final days before the election. On questions of infidelity, the White House managed only some vague denials.

The fact is, an adult film star and a former Playboy Playmate, telling their stories of hush money and accusing the president of affairs, are making it hard for the White House to move ahead or even stand straight. The mounting legal and ethical questions about campaign finance rules and “who knew what, when,” are taking the footing out from under the place.

Noticeably, except for yet another generic tweet about “fake news,” the president stayed silent on both fronts Monday, sending staff and a Cabinet member to condemn Russia on behalf of the United States and not responding directly to the televised tales about him.

The RUNDOWN with Emily Goodin

Florida’s GOP Gov. Rick Scott tweeted Monday he’ll have a “big announcement” to make on Facebook Live April 9, which political watchers took to be the date he will announce his expected challenge to Democratic Sen. Bill Nelson.

It would be a battle of the titans.

Nelson has eight million dollars cash on hand, according to FEC reports, and Scott is a multi-millionaire who has shown he’s willing to spend his own money on his political career.

The race will also become a barometer of Senate matchups, particularly on guns and school safety.

Scott became a national figure after the Feb. 14 shooting at Marjory Stoneman Douglas High School.

And the two men have already exchanged barbs about the gun issue.

In late February, Nelson criticized Scott for not appearing at a CNN town hall following the Parkland shooting in which 17 students died. And Scott replied about Nelson: “He has been in office for almost 50 years. He hasn’t done anything on gun safety or school safety, and nothing on gun control.”

The gun issue could be a tricky one for both parties as Senate candidates navigate a changing political climate and strong feelings from voters.

A lot of Democrats are on the ballot in gun-friendly states or in red states that Donald Trump carried – states where a pro-gun message was once welcomed and the norm.

And Republicans could face a new political environment where an “A” rating from the NRA is no longer a passing grade.

The TIP with John Verhovek

With the 2018 primary voting now well-underway, the national political landscape ahead of the midterm election is coming into clearer focus.

Democrats are hoping that their upset victory in the special election in Pennsylvania's 18th Congressional District is a harbinger of the coming blue wave, while Republicans are hoping to stem that tide by selling tax reform and boosting vulnerable members in races across the country.

ABC News has made a number of changes to our "18 for ‘18" key races to watch in the 2018 midterms.

Additions include an expected tight races for incumbent Democratic Sen. Claire McCaskill in Missouri, where a scandal-tarred governor is now under an investigation led by the GOP's top candidate looking to replace her, a crowded battle in Southern California to replace GOP Rep. Darrell Issa, an incumbent versus incumbent match in Democrat Conor Lamb's next race, and more. By following these new races -- and the others we have been tracking the last few months -- we hope to provide a fuller picture of the political atmosphere nationwide.

Here are the races added to the list:

California's 49th Congressional District

Illinois' 6th Congressional District

Missouri Senate

Mississippi Senate (Thad Cochran's seat)

Pennsylvania's 17th Congressional District

WHAT YOU NEED TO KNOW TODAY

QUOTE OF THE DAY

“False charges are settled out of court all the time. You have to ask Michael Cohen about the specifics.” - White House deputy press secretary Raj Shah, when asked by reporters why the president’s lawyer paid Stormy Daniels $130,000 just days before the 2016 election.

NEED TO READ

What's next for the March for Our Lives movement Hundreds of thousands of people showed up in force all across the country this weekend to demand action on gun violence in the wake of the February shooting at Marjory Stoneman Douglas High School in Florida. https://abcn.ws/2G9pFo1

Stormy Daniels not going away 'anytime soon,' lawyer says Porn actress Stormy Daniels has a "litany of more evidence" to back her allegation of an affair with President Donald Trump, her lawyer told "Good Morning America" today. https://abcn.ws/2pHSxsl

US expels 60 Russian intelligence officers in response to ex-spy's poisoning President Trump is expelling 60 Russian intelligence officers from the United States and ordered the closure of the Russian consulate in Seattle, the White House announced Monday. https://abcn.ws/2DWiKIA

Cambridge Analytica accused of violating US election laws in new legal action Amid mounting accusations that data firm Cambridge Analytica misused the Facebook data of up to 50 million user profiles, the U.K.-based firm and its top executives are now also under fire for alleged violations of U.S. election laws. https://abcn.ws/2IRFmxT

FTC opens investigation into Facebook data protections The Federal Trade Commission said it is opening an investigation into Facebook after news reports raised "substantial concerns about the privacy practices of Facebook." https://abcn.ws/2GbYlBi

Watchdog group files ethics complaints against lobbyists who joined Trump administration As many as 30 Trump administration appointees may be in violation of ethics guidelines intended to prevent officials from working in agencies they once lobbied, a government watchdog said Monday. https://abcn.ws/2I2cemb

Record GOP congressional retirements as 2018 midterms loom Congressional retirements can indicate which way the political winds are blowing. https://wapo.st/2G91N3V

The Note is a daily ABC News feature that highlights the key political moments of the day ahead. Please check back tomorrow for the latest.